Inorganic particles are expecting to play an important role in future nanotechnologies. Mineral or inorganic synthesis has advanced during the last years, in particular with respect to the development of “soft chemistry” and the systematic use of aqueous media as synthesis solvent. Particles at the nanometer length scale, i.e. with typical sizes in the range of 10 nm, are now available for many metals, including gold and platinum, and metal oxides, including cerium, titanium and iron oxides. However, substantial difficulties remain with respect to reliably producing stable particles in the submicrometric range, i.e. in the range of from about 20 nm to about 1000 nm. The submicrometric size range is interesting for many applications, including chemical mechanical polishing, anti-UV filters, and nanocomposite reinforcements. There is by now a need to fill this gap by providing inorganic colloids within the submicrometric size range in a simple and inexpensive manner.
The possibility of using inorganic nanoparticles as building blocks and of their co-assembly with polymers, for the design and fabrication of colloidal and supracolloidal assemblies has been recognized, A. K. Boal, F. Ilhan, J. E. DeRouchey, T. Thurn-Albrecht, T. P. Russell and V. M. Rotello, “Self-assembly of nanoparticles into structured spherical and network aggregates,” Nature 404, 746-748 (2000), and techniques for controlled clustering of nanoparticles have been elaborated. J. F. Berret, N. Schonbeck, F. Gazeau, D. El Kharrat, O. Sandre, A. Vacher and M. Airiau, “Controlled clustering of superparamagnetic nanoparticles using block copolymers: Design of new contrast agents for magnetic resonance imaging,” Journal of the American Chemical Society 128, 1755-1761 (2006), J. F. Berret, A. Sehgal, M. Morvan, O. Sandre, A. Vacher and M. Airiau, “Stable oxide nanoparticle clusters obtained by complexation,” Journal of Colloid and Interface Science 303, 315-318 (2006).
US 2005176863 directed to Rare Earth Aggregate Formulation Using D-Block Copolymers, and WO 2008008354 directed to Aqueous Dispersions of Hybrid Coacervates Delivering Specific Properties Onto Solid Surfaces and Comprising Inorganic Solid Particles and a Copolymer each describe processes for making nanoparticle clusters by mixing oppositely charged nanoparticles and block copolymers.
Polyelectrolyte layers have been constructed from oppositely charged polyelectrolytes, G. Decher, “Fuzzy Nanoassemblies: Toward Layered Polymeric Multicomposites,” Science 277, 1232-1237 (1997), F. Caruso, R. A. Caruso and H. Möhwald, “Nanoengineering of Organic and Hybrid Hollow Spheres by Colloidal Templating,” Science 282, 1111-1114 (1998), including stacked assemblies of alternating layers of oppositely charged polyelectrolytes, N. Laugel, C. Betscha, M. Winterhalter, J.-C. Voegel, P. Schaaf and V. Ball, “Relationship between the Growth Regime of Polyelectrolyte Multilayers and the Polyanion/Polycation Complexation Enthalpy,” J. Phys. Chem. B 110, 19443-19449 (2006).